1. Field of the Invention
The present invention generally relates to a motor vehicle state detecting apparatus or system which is employed in conjunction with a drive recorder for a motor vehicle and/or for generation of a control start signal for the control of behavior of the motor vehicle. In particular, the invention is concerned with a motor vehicle state detecting system for detecting an unstable state of behavior of the motor vehicle or a prognostic sign thereof. More particularly, the present invention is concerned with a motor vehicle state detecting system which is capable of detecting accurately an unstable state of behavior of a motor vehicle or a prognostic sign thereof with high reliability even in the case where a grip force (friction force) of tire decreases.
2. Description of Related Art
For having better understanding of the concept underlying the present invention, description will first be made of the hitherto known or conventional motor vehicle state detecting system by reference to FIG. 62 which shows in a flow chart processing operations performed by a conventional motor vehicle behavior detecting apparatus disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 277230/1995 (JP-A-7-277230) on the presumption that the motor vehicle behavior detecting system is employed in association with a motor vehicle data recording apparatus.
Referring to FIG. 62, detection of change of the condition or state of a motor vehicle is performed in steps S1 and S2.
At first, it is decided in the step S1 whether or not an anti-skid braking system (also known as antilock brake system or ABS in abbreviation) is in an activated or operating state. When it is determined in the step S1 that the anti-skid braking system is not operating (i.e., when the step S1 results in negation “NO”), decision is then made in the step S2 whether or not quick steering operation is being performed.
In this way, in the conventional motor-vehicle data recording apparatus, decision is made in the step S1 whether or not the anti-skid braking system is operated, which is then followed by the step S2 where decision is made whether or not the quick steering operation is performed.
When both the decision steps S1 and S2 result in negation “NO”, then it is decided in a step S3 whether or not a touch sensor is activated (i.e., whether or not contact of the motor vehicle with other object has occurred). When no contact has occurred (i.e., when the step S3 results in “NO”), decision is then made in a step S4 whether or not the detected value of a high-G sensor has reached or exceeded a predetermined value (i.e., whether or not collision has occurred).
In general, in the state in which the anti-skid braking system is being actuated, there is a possibility of the behavior of the motor vehicle changing rapidly. Further, when the quick steering operation has been conducted, there is a possibility that the motor vehicle has already been in an unstable state with the behavior of the motor vehicle changing rapidly.
Such being the circumstances, when either one of the decision steps S1 and S2 results in affirmation “YES”, indicating that the anti-skid braking system or the quick steering operation has been put into effect, unstable state of the behavior of the motor vehicle or the prognostic sign thereof is detected to thereby determine that there exists the possibility of collision (step S5). Thereafter, motor vehicle data is recorded and stored for a predetermined period (step S6), whereupon the processing routine shown in FIG. 62 comes to an end.
On the other hand, when the decision steps S1 to S3 results in “NO” while it is decided in the step S4 that detected value of the high-G sensor is equal to or greater than the predetermined value (i.e., when the step S4 results in “YES”), it is then determined that collision has taken place (step S7), and relevant data is then recorded and stored for a predetermined period (step S8), whereupon the processing comes to an end.
By contrast, when it is determined in the step S4 that detected value of high-G sensor is smaller than the predetermined value (i.e., when the step S4 results in “NO”), then the processing routine shown in FIG. 62 is immediately terminated.
Further, when it is determined in the step S3 that the touch sensor is activated (i.e., when the step S3 results in “YES”), it is then determined in a step S9 that collision has taken place. In that case, relevant data is recorded and stored for a predetermined period (step S10), whereupon the processing routine shown in FIG. 62 is terminated.
As is apparent from the above, in the conventional motor vehicle state detecting system, rapid change of the behavior of the motor vehicle is detected in the state where the anti-skid braking system is being applied or the quick steering operation is performed, to thereby make decision as to the possibility of occurrence of the collision.
However, in a slippery road surface condition such as typified by a snow-covered road, there may occur such situation that the motor-vehicle falls into a spinning state even when the steering operation is performed slowly without effectuating the braking operation.
In the situation mentioned above, it is impossible to detect the unstable state of behavior of the motor vehicle or the prognostic sign thereof with high accuracy and reliability through the detection procedure conducted by the conventional apparatus described above.
As is apparent from the foregoing, the conventional motor vehicle state detecting system is so arranged as to detect the unstable state of the motor vehicle on the basis of operation of the anti-skid braking system and quick manipulation of the steering wheel (steering handle). Thus, with the conventional motor vehicle state detecting system, it is difficult or impossible to detect with accuracy the unstable state of the motor vehicle on the slippery road surface condition such as the snow-covered road condition or the like, giving rise to a problem.